Voice control systems are used in a multiplicity of technical fields. In this case, the spoken words are firstly detected as sound signals, usually by one or more microphones, and are then fed to a speech recognition system. In this case, the speech recognition is usually based on an acoustic model and a speech model. The acoustic model utilizes a large number of speech patterns, mathematic algorithms being used to indicate the words which acoustically best match a spoken word. The speech model in turn is based on an analysis which uses a multiplicity of document samples to ascertain the context in which, and how often, certain words are normally used. Such speech recognition systems make it possible to recognize not only individual words but also fluently spoken sentences with high recognition rates. However, the recognition rate drops drastically when non-negligible background noises are present.
The robustness with respect to such acoustic interfering influences can be increased in various ways. Thus, in dictation systems for computers, a microphone on a headset frame is fastened directly in front of the speaker's mouth. In these systems, a very constant signal and hence an, in some instances, appreciable recognition rate can be achieved only by the direct proximity to the mouth. It is likewise known to control a television set by speaking the operational commands into the microphone which is integrated in a remote control. However, the remote control has to be held directly in front of the user'mouth in this case as well.